Using boats and helicopters to drop about 120 tons of poisoned bait, New Zealand has launched the biggest rat eradication program in history. By ridding the remote Campbell Island south of New Zealand of 200,000 rats, officials hope to clear the way for the return of the flightless teal duck and the restoration of a species of wading bird found only on the island. They won’t know for two years if the $1.1 million eradication project has been successful.